The use of homopolymers having a repeat unit represented by the structural formula: ##STR1## wherein R.sub.1 is lower alkyl of from 1 to about 6 carbon atoms, and wherein X.dbd.OH, or OM where M is a cation; for controlling the formation of mineral deposits and inhibiting corrosion in aqueous systems or surfaces exposed to aqueous systems is disclosed in U.S. Patent No. 4,446,046. The preferred polymer is poly(isopropenylphosphonic acid) (PIPPA: R.dbd.CH.sub.3, X.dbd.OH). The preparation of PIPPA is disclosed therein as beginning with the preparation of isopropenylphosphonic acid (IPPA) by a reaction mechanism involving the nucleophilic addition of PCl.sub.3 to the carbonyl group of a compound corresponding to the desired alpha-beta ethylenically unsaturated phosphonic acid. Upon isolation of the desired monomer, radical chain addition polymerization in bulk, suspension, solution, emulsion or thermal polymerization form is undertaken.
The polymerization of IPPA is exemplified in '046 by both non-aqueous and aqueous procedures. In the non-aqueous suspension polymerization procedure, the IPPA is dissolved in an organic solvent, polymerized by addition of an organic soluble initiator, the crude polymer is isolated by filtration, washed with acetone, and purified by vacuum stripping to remove residual volatile organics to yield a water soluble solid. The aqueous solution polymerization procedure involves treating an alkaline aqueous solution of IPPA with a water soluble polymerization initiator such as ammonium persulfate.
The aqueous polymerization methods are preferred from an economic standpoint since they do not incorporate the use of costly organic solvents and the time intensive separation and purification (with respect to volatile organics) operations associated with the non-aqueous preparation methods. Conversion to PIPPA for the prior art aqueous procedures, however, are typically limited to about 60%, even with high initiator addition; whereas the non-aqueous methods provide conversions of approximately 80%.